1. Field of the Invention
The present invention relates to a spindle device for machine tools that is equipped with an unclamping cylinder mechanism for moving a drawbar in an unclamping direction. The drawbar biases a tool fit into the tool spindle.
2. Discussion of the Related Art
An unclamping cylinder mechanism has been used in a spindle device for unclamping a tool fit into a tool spindle. Conventionally the unclamping cylinder mechanism has been provided with a cylinder block having a hydraulically driven piston that is tightened to a rear end wall of a tool headstock and it serves to pivotally support the tool spindle. This is done by means of a plurality of bolts with a gap provided against the tool spindle. Further a hydraulic passage in the tool spindle body and a hydraulic passage in the cylinder block are connected to each other by means of hydraulic piping.
In such a spindle device, generally, the whole unclamping cylinder mechanism is removed from the tool spindle body for maintenance or replacement of the tool spindle. In this state, the tool spindle is pulled out forward, due to interference with other working tools and the structure of the component parts.
However, in such a conventional structure, when the whole unclamping cylinder mechanism is removed, bleeding air from the hydraulic piping is necessary to refit the unclamping cylinder mechanism to the tool spindle body. This requires labor and time to perform this task and it represents a problem. Also, since the conventional structure involves removing and refitting the unclamping cylinder mechanism which is heavy, the operator is burdened with a laborious task and this results in a lower work efficiency that is considered another problem.
The present invention has been made considering the above mentioned problems in the prior art. An object of the present invention is to provide a spindle device for machine tools that can eliminate the need for the laborious air bleeding work and the labor-demanding removing/refitting work.
In order to achieve the above object, the present invention provides a spindle device for a machine tool, comprising a tool spindle body having an axial hole therein; a drawbar movably disposed in the axial hole of the tool spindle body for biasing a tool in a clamping direction; and an unclamping cylinder mechanism provided at a rear portion of the tool spindle body for moving the drawbar in an unclamping direction. The unclamping cylinder mechanism includes a cylinder block having a hydraulic passage therein. The cylinder block is connectable to a rear end wall of the tool spindle body with a plurality of bolts. Further, a relay oil passage is partially disposed in one of the plurality of bolts for allowing hydraulic fluid to communicate with the hydraulic passage in the cylinder block. The unclamping cylinder mechanism is supportable by one of the plurality of bolts so as to be pivotable between a locked position and a released position. The unclamping cylinder mechanism can be pivotable on a locking bolt.
To remove the tool spindle of the invention, bolts other than the locking bolt having the relay oil passage therein are loosened and removed, and then the whole unclamping cylinder mechanism is pivoted about the locking bolt to the retreat or released position. As a result, while the unclamping cylinder mechanism remains supported on the tool spindle by the locking bolt, a rear end portion of the tool spindle is exposed. In this state, the tool spindle is pulled out forward. On the other hand, for refitting of the unclamping cylinder mechanism, the whole unclamping cylinder mechanism is pivoted to the original locked position about the locking bolt and then the removed bolts are tightened and locked.
According to the spindle device of the invention, the relay oil passage, for making the hydraulic passage in the cylinder block and the hydraulic passage in the tool spindle body communicate with each other, is formed in one locking bolt out of the plurality of bolts. The unclamping cylinder mechanism is supported by the locking bolt so as to be pivotable between the locked position and the released position. Therefore, the removal work of the tool spindle can be achieved while both the hydraulic passages of the tool spindle body and the cylinder block are kept in communication with each other and while the whole unclamping cylinder mechanism is supported on the tool spindle body. As a result, the need for bleeding air during refitting the unclamping cylinder mechanism can be eliminated. Further the labor demanded of the operator can be reduced compared to when the whole unclamping cylinder mechanism is removed outwardly and refitted as in the conventional case described above. Thus, the present invention can improve the working efficiency for maintenance and replacement of the tool spindle.
Also, since the hydraulic passage in the tool headstock and the hydraulic passage in the cylinder block communicate with each other via the relay oil passage of the locking bolt, the need for conventional hydraulic piping can be eliminated. This allows a reduction in the number of parts as well as a simplification in the structural arrangement as further advantages of this invention.